Calcination retort



J1me 1964 c. A. BLESCH ETAL 3,136,273

CALCINATION RETORT Filed Jan. 28, 1959 7 Sheets-Sheet 2 1 I //I//////////I/I/ /I////// Ill I,

N INVENTOR. Charles A. Blesch BY Clark K. Benson Attorneys June 9, 1964 c. A. BLESCH ETAL 3,135,273

CALCINATION RETORT Filed Jan. 28, 1959 '7 Sheets-Sheet 3 BY Clark K. Benson Attorneys June 9, 1964 c. A. BLESCH ETAL CALCINATION RETORT 7 Sheets-Sheet 4 Filed Jan. 28, 1959 INVENTOR. Charles A.Blesch Clark K. Benson Attorneys June 9, 1964 Filed Jan. 28, 1959 c. A. BLESCH ETAL 3,136,273

CALCINATION RETORT 7 Sheets-Sheet 5 INVENTOR. Charles A. Blesch Clark K. Benson ZZZ GDQZS Attorneys June 9, 1964 c. A. BLESCH ETAL CALCINATION RETORT '7 Sheets-Sheet 6 Filed Jan. 28, 1959 .mn s m m. m W Z m K r a hm 66 M Y B 8 0 June 9, 1964 c. A. BLESCH ETAL CALCINATION RETORT Filed Jan. 28, 1959 7 Sheets-Sheet '7 INVENTOR. Charles A. Blesch Clark K. Benson Attorneys United States Patent O 3,136,273 CALCINATION RETORT Charles A. Blesch, Bnrlingarne, and Clark K. Benson,

San Francisco, Calif, assignors to No Flame Process,

Inc, Miami, Fla, a corporation of Florida Filed Jan. 28, 195%, Ser. No. 789,706

1 Claim. (Cl. 110-3) This invention relates generally to a method and apparatus for calcinating or cremating bodies and more particularly to calcinating bodies without visible flame.

Cremation is gaining very rapidly in certain sections of the United States. Long range forces such as the greatly increasing population, the unavailability of land for cemeteries and the like indicate that a more accelerated rate of growth of cremations in the United States awaits only adequate and attractive facilities which can be utilized to educate thepublic. Calcination or cremation has been found to be much less repugnant to the nearest of kin when it is carried out without visible flame. One method and apparatus proposed for accomplishing such no-fiame cremation is described in Patent No. 2,365,983. The method therein described consists of placing the cadaver within a chamber free of oxygen and then subjecting the chamber to high temperatures to drive off the volatiles which are piped and burned in a separate furnace. volatiles have been driven off, the carbon is consumed in the presence of oxygen by applying a higher temperature to the chamber leaving the conventional mineral ash. Great difficulty has been found in implementing this method because the apparatus described in Patent No. 2,365,983 has been found to be impracticable. The calcination or destruction of the body has been found to be very slow and often incomplete. In addition, the apparatus required considerable manual supervision throughout After the i the calcination. To make such a method cremation com- .the visible flame which will enable such an operation to be carried out economically and expeditiously.

Another object of the invention is to provide a calcination retort of the above character in which the gases are generated under a positive pressure introduced at high velocities into the calcinating chamber. 7

Another object of the invention is to provide a calcination retort of the above character in which the gases are maintained in a turbulent state within the calcinating or cremating chamber. A Another object of the invention is to provide a calcinating retort of the above character in which a substantial amount of heat is transferred by conduction and radiation to the cremating chamber.

Another object of the inventionis to provide a cremation retort in which the escape of obnoxious gases is inhibited by creating negative pressure within the calcinating chamber. v

Another object of the invention is to provide a calcina: tion retort of the above character in which flameless,

. smokeless and odorless cremation is automatically carried 3,136,273 Patented June 9, 1964 at a predeterminedtemperature to combust all volatiles and destroy any obnoxious odors.

Another object of .the invention is to provide a calcination retort of the above character in which all volatiles are completely destroyed before entering the fan for inducing the draft. 7

Another object of the invention is to provide a calcination retort of the above character in which cold air is bled into the fan to reduce the temperature of the gases passing through the fan. 3 u

Another object of the invention is to provide a calcination retort of the above character in which the negative pressure on the calcination chamber is regulated by the cold air bleed for the fan.

Another object of the invention is to provide a calcination retort of the above character in which the gases containing volatiles must pass through a labyrinth which insures complete combustion of all volatiles in the gases.

Another object of the invention is to provide a calcination retort of the above character in which a positive pressure type door seal is utilized to prevent the leakage of gases from the retort and the leakage of air into the retort.

Another object of the invention is to provide a calcination retort of the above characterin which the door is remotely operated. I

Additional objects and features of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

FIGURE 1 is a front elevational view of a calcination retort incorporating the present invention showing the door in a partly open position.'

FIGURE .2 is a partial side elevational view looking along the line 22 of FIGURE 1.

FIGURES is a cross-sectional view taken along the line 33 of FIGURE 1.

FIGURE 4 is a cross-sectional view taken along the line 4-4 of FIGURE 1.

FIGURE Sis a cross sectional view taken along the line 55,of FIGURE 1.

FIGURE 6 is an enlarged detailed View showing the door construction.

FIGURE 7 is a cross-sectional view taken along the line 77 of FIGURE 4.

FIGURE 8 is across-sectional view takenalohg the line 8+8 of FIGURE 4.

FIGURE 9 is a side elevational view of the exhaust fan.

FIGURE 10 is a schematic diagram of the piping and control system forIh'ecalcination'retort. In gene'raL'the present invention consists of generating heatedgases having a controlled'oxygen content under a positive pressure away from the body,..and then introducing the heated gases at high velocity jet streamsto cause turbulent motion of the heated gases about the body and permitting a substantial amount of heat to pass to the body by conduction and radiation from .the. zone in which the heated gases are generated, the temperature of the body being raised by the heated gases and the heat passingthrough the body by conduction and radiation to drive off the volatiles from the-body and reduce the body to a mineraLash. "The oxygen content of the gases is insuflicient to permit the body to burst into flame. The volatiles driven off from "the body are conveyed away from the body and combusted in a separatezone removed from the body at a predetermined temperature to ensure any obnoxious odors. The zone about the body is main taine'd under a negative pressure to inhibit the escape of obnoxious odors from" the body during cremation.

; x The cremation is carried out in a gas-tight chamber with i a positively sealed opening. r

'door 18 hereinafter described in detail.

Referring to the drawings, the calcination retort illus trated therein is constructed primarily of fire brick of various types well known to those skilled in the art. The fire brick in various portions of the calcination retort differs in quality depending upon the temperature which is encountered by the firebrick. Normally, the inner walls of the retort are'constructed of a refractory brick, whereas the intermediate and outer walls are formed of an insulated fireproof brick. The fire brick forming the retort is completely enclosed within a gastight metal casing 11 which is'supported by top, bottom and side structural members 12.

As will be noted-from the drawings, the retort has been constructed with three superimposed chambers or zones 13, 14 and 16. For purposes of convenience, the lowermost chamber or zone 13 will be termed the generating chamber, and the intermediate chamber14 will be designated as the calcinating or cremating chamber. The uppermost chamber 16 will be designated as the combusting chamber.

The loading or front end of the retort is provided with an opening 17 which opens into the cremation chamber 14 and which is adapted to be opened and closed by a Four flues 19, 21, 22 and 23 are provided near the front end of the retort and lead from the opposite sides from the top of the generating chamber 13 into the bottom of the cremating chamber 14 and enter the cremating chamber 14 through openings 24 which enter the chamber 14 from opposite sides. The openings for the flues 19 and 21 are staggered with respect to the openings for the fiues 22 and 23.

An opening 26 is provided in the bottom rear wall of the chamber 14 and leads into a flue 27 which extends upwardly into the chamber 16. The flue 27 leads into a Venturi-like throat 28 centrally disposed at the rear end of the chamber 16. A centrally disposed. baffle 29 in chamber 16 is spaced away from but in front of the discharge endof the throat 28. It is provided with a small centrally located opening 31 for a purpose hereinafter described. A plurality of bafiies 32 are disposed longitudinally of the chamber 16 from opposite side walls forming the chamber 16. The baflles extend from the top to the bottom of the chamber and each extends laterally a distance substantially greater than one-half the width of the chamber. The bafiies on the opposite side walls are staggered with respect to each other and form a labyrinthine passageway through the chamber 16 as shown particularly in FIGURE which leads into a vertical flue opening 34.

Suitable heating means is provided for the chamber 13 and consists of a burner 36 which is mounted in the rear wall of the chamber 13. Aviewing aperture 57 is provided in the front wall of the chamber 13 so that operation of the burner 36 can be observed. a

The cremation chamber 14- is separated from the generating-chamber 13 by a thin wall '38 of suitable conducting material such as silicon carbide tile.

Suitable heating means is also provided for in the chamber 16 and consists of a burner 41 aligned with the throat 28 and mounted in the rear wall of the chamber 16.- A plurality of laterally spaced air nozzles 42 are mounted below the burner 41 in the rear wall forming the chamber 16. They are inclined at an angle so that the air introduced therefrom enters the heated gases from the burner 41 for a purpose hereinafter described.

A thermocouple 43 is mounted in one side wall forming the chamber 16 approximately midway between the ends of the chamber. i

Aplurality'of rollers '46 are disposed within the crema tion chamber- 46 and rest upon ledges 47 providedwithin the chamber The rollers 46 roll upon the ledges 47 and facilitate insertion of the casket containing the body. An additional charging roller 48 is mounted on the front of the re'tor'tina manner hereinafter described. I it suitable material such as asbestos.

The door 18 closing the opening 17 leading into the cremating chamber is formed of a suitable cast refractory which is covered with a metal casing 49. A viewing aperture 51 is provided in the door. The door 18 also includes a metal framework 52 which is provided with a U-shaped channel 53 which extends around the inner surface of the outer' perimeter of the door. Suitable gasket means is mounted in the U-shaped channel and, as shown, can consist of a pair of members 54 of suitable material such as asbestos which are carried by the channel.

One of the structural members 12 for the retort carries the door jam 56 which includes a U-shaped member 57 that is mounted on the front of the retort and which extends around the opening 17 provided in the retort. The U-shaped member 57 carries suitable gasket means such as the square gasket member 58 also formed of The gasket member 53 and the gasket members .59 are adapted to form a pressure-tight seal as hereinafter described.

A pair of bars 61 are mounted in the framework 52 and extend transversely of the framework. The ends of the bars are provided with rollers 62 which are accommodated within a pair of substantially vertical U-shaped channel members 63 disposed on opposite sides of the opening 17. The upper ends of the channel members 63 are pivotally connected to links 64 that are pivotally connected to brackets 66 mounted upon a pair of vertical posts 67. The posts 67 form an integral part of the structure of the retort and are mounted on opposite side walls of the retort. The lower ends of the channel members 63 are adapted to swing freely between the innermost and outermost positions as determined by U-shaped members 68 secured to the front wall of the retort.

Suitable means is provided for moving the channel members 63 and the door 18 carried thereby between sealed and unsealed positions of the door and consists of a pair of spaced U-shaped members 71 mounted on each of the channel members 63. The members 71 are pivotally connected to the operating rods of suitable actuating means such as fluid cylinders 73 carried by the casing 11 of the retort. The actuators 73 are mounted in such a manner that the door is moved horizontally between sealed and unsealed positions as hereinafter de scribed.

Suitable means is provided for raising and lowering the door and consists' of a pair of elongate elements or chains 76 which are secured to the top bar 61 of the door. The chains. have their upper ends secured to the sprocket wheels 77 aflixed to a horizontal shaft 78 rotatably carried by the posts 67. Suitable means is provided for rotating the shaft 78 and consists of another sprocket wheel 79 mounted on the shaft 78. An elongate element or chain 31 has one end secured to the sprocket wheel 79 and the other end connected to the operating rod 82 of a suitable actuator such as a fluid cylinder 83 which is also mounted on the casing 11.

The flue opening 34 is connected to an exhaust fan assembly 91 which ismounted in a suitable manner'such as on the roof of the structure which houses the calcination retort. More indetail, the duct 34 is connected to a vertical stack 92. The stack 92 is provided with a horizontal extension 93 which feeds into one side of the exhaust fan'housing '94. The exhaust fan (not shown) is mounted within the housing 94 and is driven by a motor 6. The exhaust fan exhausts the gases through a'vent which is formed by verticalextension 97 of the housing 94. A protective covering 5% is mounted-above the vent. The exhaust fan and the stack are. provided with suitable insulation in: a manner well known to those skilled in the art to prevent'the exterior walls of the fan assembly from becoming too hot, from the gases passing through the stack 92 and which is providedwith inlet opening 162 in its bottom end. A damper 106 is pivotally mounted within the housing 101 and is adapted to regulate the flow of cold air into the fan for a purpose hereinafter described.

Suitable means provided for controlling the operation of the calcination retort is shown schematically in FIG- URE 10. An air supply is provided for both burners 36 and 41 through piping 111. The piping 111 is connected to one side of a butterfly valve 112 by piping 113, and the other side of the valve is connected to the burner 36 by piping 114. Piping 111 is connected to one side of a valve 116 by piping 117, and the other side of the valve is connected to the burner 41 by piping 118. The air supply is also connected to one side of a valve 119 by piping 121, and the other side of the valve 119 is connected to the air nozzles 42 by piping 122.

Gas or fuel is supplied through piping 126. Piping 126 is connected to one side of a valve 127 by piping 128, and the other side of the valve 127 is connected to the burner 41 by piping 129. The piping 126 is also connected to one side of a valve 131 by piping 132, and the other side of the valve is connected to the burner 36 by piping 133.

The valves are controlled in a suitable manner to effect substantially automatic operation of the calcination retort. Valve 112 is operated by suitable means such as a crank unit or cylinder 136. The crank cylinder 136 is controlled by the regulator 137. The crank unit 136 can be of any suitable type such as the type 60K manufactured and sold by the Askania Regulator Company, and the regulator 137 can also be of any suitable type such as one of the regulators manufactured and sold by the Askania Regulator Company. The valve 131 is manually set. The same is true for the valve 119. Valve 127 is controlled by a pyrometer 141 which is connected to a thermocouple 43 by conductor 142. Valve 116 is controlled by a ratio controller 144 so that the valve 116 is regulated to maintain the desired ratio of air to gas as the valve 127 is controlled by the thermocouple 143.

Operation of our calcination retort in practicing our method may now be described as follows: The casket containing the body is loaded into the calcination retort through the opening 17 by placing the rear end of the casket upon the charging roller 47. The casket is then pushed inwardly and allowed to rest upon the rollers 46.

After the body and casket has been inserted in the calcination chamber 14, the calcination retort is purged of any combustible gases or the like which may remain in the chamber by first passing air through the various chambers of the calcination retort.

After this has been accomplished, the top burner 41 is ignited and chamber 16 is brought up to a predetermined operating temperature. As soon as this temperature is reached, the door 18 is closed by first lowering the door 18 by operation of the cylinder 83. As soon as the door 1 has reached its lowermost position, the cylinders, 73 are operated to pull the channels 63 inwardly toward the opening carrying with them the door to firmly urge the door seals 54 into engagement with the seal 58 carried by the retort itself. This provides a positive door seal for the calcination retort. It will be appreciated that the pressure applied by the fluid actuators 73 will be substantial and, therefore, a very positive seal is obtained to close the opening in the cremation retort. This seal is very important as hereinafter explained.

Burner 36 is then ignited and the valve 131 is set to apply apredetermined quantity of B.t.u. to the generating chamber. The control units 136 and 137 serve to automatically proportion the air which is supplied to the burner 36 so that a relatively precise combustible mixture is supplied to the burner. The ratio of air is so controlled that substantially all of the oxygen in the air is utilized in combusting the fuel which is supplied to the burner 36. The hot gases which are formed in the generating chamber 13 are formed under a positive pressure and sweep along the entire length of the generatihg chamber 13 and come into intimate contact with the bottom surfaces of the silicon carbide tiles 38 which separate the chamber 13 from chamber 14. The hot gases, after passing through the chamber 13, pass into the lines 19, 21, 22 and 23' disposed on opposite sides of the chamber 13. The gases are exhausted through the openings 24 into the chamber 14 as relatively high velocity jet streams because of the differential in pressure between the chambers 13 and 14. Chamber 13 is normally maintained under a positive pressure, whereas the chamber 14 is normally maintained under a negative pressure. The negative pressure on chamber 14 is obtained by the induced draft from the exhaust fan as hereinafter described. The amount of negative pressure is regulated by controlling the damper 1116 in the fan assembly.

As hereinbefore pointed out, the openings in one side wall are staggered with respect to the outlet openings in the other side wall of the chamber 14 so that the jet streams passing therefrom do not directly buifet each other. Also, it will be noted that the hot gases are introduced near the front and bottom portions of the chamber 14 to prevent the formation of cold spots in the chamber. The hot gases rise and swirl about the casket and body and come into intimate contact with the casket and body because of the turbulent motion of the gases. As they rise, they pass rearwardly through the chamber 14 and are caused to wipe the top surfaces of the silicon carbide tiles 38 so that they are heated by the silicon carbide ti es.

The thin wall 38 serves to form a relatively pressuretight barrier between the chambers 13 and 14. Since it is formed of a heat conducting material, a substantial amount of heat is conducted from the chamber 13 to the chamber 14 to greatly accelerate the calcination or cremation of the body and casket in the chamber 14.

The turbulent circulating hot gases passing from the chamber 13 into the chamber 14 and the passage of heat through the heat conducting wall 38 soon cause the produetion of moisture and volatiles in the chamber to reduce the contents to a mineral ash. The oxygen content of the gases entering the chamber 14 from the chamber 13 is rigidly controlled so that the free oxygen in the calcination chamber 14 is insuflicient to support combustion in chamber 14 that will produce flame. Although no visible flame rises from the chamber contents being cremated, the contents within the chamber 14 may reach a temperature at which the contents will glow with a bright red color. However, at no time is a resemblance of a flame produced. Y

The vapors and volatiles that are driven off from the contents of the chamber 14 move downwardly to the rear of the chamber 14 through the discharge opening 26 provided in the lower portion of the rear wall forming the chamber 14. p x

These vapors and volatiles together with the other gases exhausted from the chamber 14 pass upwardly through the flue 27 into the combusting chamber 16. These gases, as they pass upwardly and pass into the flame from the burner41, are thoroughly mixed with a substantial quantity of excess air provided by the nozzles 42. These gases, vapors and volatiles then pass into a continuously expanding igniting throat 28 in which all or substantially all of the combustible vapors and volatiles are ignited. The gases discharging from the throat 28 impinge upon the baflie 29 which is disposed in front of the throat. These hot gases serve to heat the baffle 29 to a high temperature so that the baflie 29 acutally forms a hot spot immediately in front of the throat. This hot spot serves to ensure that all the combustible vapors and volatiles in the gases passing through the throat are ignited. .Certain of the hot gases pass through the centrally disposed small opening 31 provided in the fbaffle 29. The remainder of the gases are deflected to create turbulence and a thorough mixing of all the gases to ensure combustion of all volatiles and vapors in the gases. The gases then pass around the outer ends of the baflle' 29 and move towards the front of the chamber 16 by passing through the labyrinth formed by the laterally disposed bafiles 32. The baffles 32 provide radiant scrubbing surfaces which cause additional mixing and heating of the gases to ensure complete incineration of all unburned combustible components. In addition, they ensure destruction of all obnoxious odors before they pass into the discharge flue opening 34. The excess of air provided by the nozzles 42 ensures that there is sufficient oxygen in the gases to make possible combustion of all the combustible components in the gases passing through the chamber 16.

Sincethe baffles 32 extend from the top to the bottom of the chamber 16, it is impossible for the gases to float through the chamber 16 without coming into contact with the radiant scrubbing surfaces provided by the bafiies 32. The temperature of the chamber 16 is continuously monitored by the thermocouple 43 which in conjunction with the pyrometer 141 controls the B.t.u. output from the burner 41 so that the chamber 16 is maintained at a predetermined temperature to ensure combustion of all combustible components in the gases'and also to ensure destruction of the obnoxious odors in the gases. 7 The quantity of air supplied to the burner 41 is controlled by the controller 144- so that the ratio of air to the gas is such that a hot flame is at all times produced by the burner 41.

The gases passing from the exhaust flue 34 pass into the stack 92 of the exhaust fan assembly and are sucked into the exhaust fan and exhausted through the venting structure 97. Before the hot gases are taken into the fan, a certain amount of cold air is mixed with the gases by the cold air bleeder structure 101. The amount of cold air introduced is controlled by the damper 1%.

The cold air introduced into the gases reduces the temperature of the gases which enter the fan, and, therefore, reduces the operating temperature required for the fan.

The damper 106, in addition to controlling the amount of cold air introduced into the exhausted gases, also serves to control the negative pressure which is maintained in the calcinating chamber or zone 14. This negative pressure is maintained to create a pressure differential between the chambers 13 and 14 so that the gases enter the chamber 14 as relatively high velocity jet stream. The high velocities of the jet streams are due to the pressure from the combustion air which is supplied to the burner 36 and is not dependent upon the negative air pressure in the calcination chamber. The negative pressure is also maintained within the chamber to inhibit the. escape of any obnoxious odors from the calcinating'chamber 14 through the door seal. The casing 11 surrounding the calcination retort is gas-tight and, therefore, the only opportunity for leakage'is through the sealbetween the door and the calcination retort. The positive pressure applied to the door seal effectively prevents any leakage into or out of the calcination chamber 16.

By way of example, one calcination retort constructed in accordance with the above invention was operated with temperatures in chamber 13 ranging from 1500 to 2000" F and with a positive pressure ranging from 2 to,;6'inches of 1 water above atmosphere. The burner 35 for the chamber 13 was operated at a fixed firing rate by adjustthe entrance of'the heated gases into the chamber 1 4 as high velocity jet streams. The blower air supplied to the found that-the temperature of the generating chamber 13 gradually increased until the maximum temperature was reached which was approximately 2000 F. The calcinating chamber 1% was operated at a negative pressure equal to a column of water from .1 to .5 inch below atmosphere. It was operated in a temperature range from ambient to 1400l600 F. It was found that over onehalf of the heat passing into the calcinating chamber 14 passed from the chamber 13 through the heat conducting silicon carbide separating wall 38. The remainder or the heat entering the chamber 14 was carried by the hot gases-emerging from the openings 24. It was found that the gases were exhausted from the openingsZd at a rate varying from 4000 to 6000 feet per minute. The comtion chamber 16 was operated at temperatures ranging from 1200 to 1500 P. However, it was found that it was preferable to operate the chamber 16 at approximately 1400 F. to ensure destruction of all obnoxious odors.

It will be apparent from the foregoing that we have provided an effective method and apparatus for cremating a body without flame. The calcination retort provides flameless, smokeless and odorless cremation automatically without depending upon the skill of the operator. It is self-contained, sets on floor level and does not need underground flues. The motorized induced draft eliminates the need for a high stack to create a natural draft. This mechanical draft also makes operation independent of varying local atmospheric conditions. The entire structure is of air-tight fabrication to contain the positive and negative pressures desired in the various chambers. The fuel-air mixtures introduced in the chamber 13 are accurately controlled by metered volumes which, in turn, provides the no-flame character of the calcination carried out in the chamber 14. Only the glow of radiant temperatures is visible in zone 14. There is absolutely no flame. The negative pressure maintained 'in the calcination chamber together with the positive pressure door seal prevents the escape of obnoxious odors. The volume of gases entering the combustion chamber is positively controlled by the input from the chamber 13 and, therefore, the usual ditficulties of excessive, uncontrolled combustion rates are avoided and the attending smoke and odor problem is entirely eliminated.

The doorfor the. calcination retort can be readily moved between open and closed positions. By first breaking the seal before moving the door upwardly or downwardly, long-life is assured for the door seal. The unit itself makes feasible practically noiseless cremation winch makes possible a dignified operation. I

This application is a continuation-in-part of application Serial No.'519,746, filed July 5, 1955, now abandoned. i

We claim:

in a calcination retort, a calcinating chamber adapted a receive a body and having an opening in one wall thereof, a door closing said opening, a heat generating chamber, burner meansdisposed in one end of said heat generating chamber, means to'feed a controlled mixture of air and fuel to said burner means to produce under a posi tive pressure ranging from 2 to 6 inches of water above atmospheric pressure a combustion product of heated gases having'a temperature ranging from 1500 to 2000 F. and having a controlled oxygen content, flue means connecting the generating chamber to the calcinating chamber, the heated gases produced in the generating chamber passing directly from the generating chamber,

' through the flue means directly into the calcinating chamher as a plurality of high velocity jet streams, means for creating a negative pressure in'the calcinating chamber ranging from .l'to .5 inch of water below atmospheric pressure, the high velocity jet streams being produced primarily by the positive pressure in the generating chamber, theoxygen content of the heated gases in the calcinating chamber being insuflicient to support a flame, a combusting chamber, flue means connecting the calcinating chamber to the combusting chamber, the heated gases in the calcinating chamber having a temperature of over 1400" F. and serving to heat the body disposed in the calcinating chamber to drive off the volatiles from the body and reduce the body to mineral ash, and means for combusting the volatiles as they are introduced into the combusting chamber from the calcinating chamber, the volatiles and the heated gases being confined in the calcinating chamber before removal of the volatiles and heated gases for combustion of the volatiles in the combusting chamber, wherein the calcinating chamber is superimposed on the heat generating chamber and wherein a thin wall of material having relatively good heat conducting characteristics in comparison to the material util'med for forming the remainder of heat generating chamber and the calcinating chamber separates the heat gencrating chamber from the calcinating chamber, said thin wall of material serving to conduct a relatively large portion of the heat passing into the calcinating chamber.

References Cited in the file of this patent UNITED STATES PATENTS 771,412 Brett et a1. Oct. 4, 1904 1,628,274 Robinson May 10, 1927 1,773,256 Breitwieser Aug. 19, 1930 1,859,300 Krenz May 24, 1932 2,625,121 Vanderwerf Jan. 13, 1953 2,714,359 Seaver Aug. 2, 1955 2,744,477 Hartley et al. May 8, 1956 2,910,022 Tinker Oct. 27, 1959 FOREIGN PATENTS 8,427 Great Britain 1901 

